intro
Purpose:
- Preliminary look at hi/lo multivariate contrast (cross-validated euclidean) in each task.
- Preliminary qualitative comparison of effects of prewhitening and pattern standardization on multivariate contrast.
Notes on analyses:
Target TRs:
- Axcpt: 7, 8, 9
- Cuedts: 9, 10
- Stern: 11, 12
- Stroop: 2, 3, 4
Contrasts (cross-validated euclidean):
- Axcpt: \(\text{BY} - \text{BX}\)
- Cuedts: \((\text{InConSwitch} + \text{InConRepeat} - \text{ConSwitch} - \text{ConRepeat})/2\)
- Stern: \(\text{LL5RN} - \text{LL5NN}\)
- Stroop: \((\text{PC50InCon} + \text{biasInCon} - \text{PC50Con} - \text{biasCon})/2\)
Transformations:
- “whitened”: spatially pre-whitened cross-validated euclidean (‘mahalanobis’)
- using vertex-by-vertex inverse covariance matrix derived from residual timeseries
- “unwhitened”: not spatially pre-whitened
- all results considered here use unstandardized euclidean distance (i.e., patterns are not z-score normalized).
Plotting and statistical details:
- within ‘curves’ sections, ribbons indicate 95% CI of bootstrapped mean beta across subjects (one ribbon per run).
- all p-value corrections were performed whole-cortex, with FDR.
- for “stats and maps” sections, HLM was used to estimate t-statistics on the hi-lo contrast per ROI:
- random-intercept models
- level-I: (TR within target window)*(run)
- level-2: subject
- \(\beta_{ts} = b_0 + d_s + \epsilon_{trs}\)
- $_{ts} is HiLo contrast per subject, tr
- \(t, s\) are indices for TR, and subject
- \(d\) is is subject-specific intercept
- \(\epsilon\) is error
Network-level contrasts
Estimates are first averaged across parcels within network per subject. Group-level stats and plots are then displayed at the network-level.
Parcel-level contrasts
counts of significant effects per TR
Using t-test of subject parcel means.

DMCC55B univariate ROIs
Curves for conjunction ROIs defined in univariate_group.rmd.
DMCC55B multivariate ROIs: Cross-task conjunction
Here conjunction analysis is performed by feeding TR-level contrast estimates to an HLM (see description at beginning of doc).
Number of parcels identified, and parcel names:
- No parcels ID’d (pFDR<0.05) in all four tasks in either whitened or non-whitened measures.
- Parcels ID’d in =>2 tasks with unwhitened: LH_Cont_Par_1, LH_Cont_Par_2, LH_Cont_Par_3, LH_Cont_Par_4, LH_Cont_Par_5, LH_Cont_Par_6, LH_Cont_pCun_1, LH_Cont_PFCl_1, LH_Cont_PFCl_2, LH_Cont_PFCl_5, LH_Cont_PFCl_6, LH_Cont_PFCl_7, LH_Cont_PFCl_8, LH_Cont_PFCmp_1, LH_Cont_PFCv_1, LH_Default_Par_5, LH_Default_Par_6, LH_Default_PFC_1, LH_Default_PFC_10, LH_Default_PFC_12, LH_Default_PFC_13, LH_Default_PFC_17, LH_Default_PFC_20, LH_Default_PFC_21, LH_Default_PFC_24, LH_Default_PFC_5, LH_Default_PFC_7, LH_DorsAttn_FEF_1, LH_DorsAttn_FEF_2, LH_DorsAttn_FEF_4, LH_DorsAttn_Post_10, LH_DorsAttn_Post_12, LH_DorsAttn_Post_4, LH_DorsAttn_Post_6, LH_DorsAttn_Post_7, LH_DorsAttn_Post_9, LH_DorsAttn_PrCv_1, LH_SalVentAttn_FrOperIns_3, LH_SalVentAttn_FrOperIns_5, LH_SalVentAttn_FrOperIns_7, LH_SalVentAttn_FrOperIns_9, LH_SalVentAttn_Med_1, LH_SalVentAttn_Med_4, LH_SalVentAttn_ParOper_2, LH_SalVentAttn_ParOper_4, LH_SomMot_9, LH_Vis_22, LH_Vis_28, LH_Vis_30, RH_Cont_Par_2, RH_Cont_Par_3, RH_Cont_Par_5, RH_Cont_Par_6, RH_Cont_PFCl_10, RH_Cont_PFCl_11, RH_Cont_PFCl_12, RH_Cont_PFCl_13, RH_Cont_PFCl_14, RH_Cont_PFCl_4, RH_Cont_PFCl_5, RH_Cont_PFCl_6, RH_Cont_PFCl_7, RH_Cont_PFCl_9, RH_Cont_PFCmp_2, RH_Cont_PFCv_1, RH_Default_Par_4, RH_Default_PFCdPFCm_10, RH_Default_PFCdPFCm_11, RH_Default_PFCdPFCm_12, RH_Default_PFCdPFCm_13, RH_Default_PFCdPFCm_9, RH_Default_PFCv_3, RH_Default_PFCv_4, RH_DorsAttn_Post_8, RH_DorsAttn_PrCv_1, RH_SalVentAttn_FrOperIns_5, RH_SalVentAttn_FrOperIns_8, RH_SalVentAttn_Med_1, RH_SalVentAttn_Med_4, RH_SalVentAttn_PFCl_1, RH_SalVentAttn_TempOccPar_3, RH_SalVentAttn_TempOccPar_5, RH_SalVentAttn_TempOccPar_7, RH_SomMot_7, RH_Vis_20
- Parcels ID’d in =>2 tasks with whitened: LH_Cont_Par_3, LH_Cont_PFCl_6, LH_Cont_PFCl_8, LH_Cont_PFCmp_1, LH_Default_Par_5, LH_Default_Par_7, LH_Default_PFC_13, LH_Default_PFC_24, LH_Default_PFC_7, LH_DorsAttn_PrCv_1, LH_SalVentAttn_FrOperIns_5, RH_Cont_PFCl_7, RH_Default_Par_1, RH_Default_PFCv_4, RH_SalVentAttn_FrOperIns_5, RH_SalVentAttn_TempOccPar_7, RH_SomMot_2
intersection of parcels ID’d by unwhitened and whitened measures in =>2 tasks
all parcels

maps (target TRs)
Unthresholded and thresholded t-statistics displayed on inflated brains. Threshold at fdr-corrected p-value (across all parcels) of 0.05. Note: colors are reverse-scaled, i.e., dark == strong effect, light == weak effect (so strong effects show up on white background).